Insulated coils for electrical machines

ABSTRACT

An insulated conductor or conductor bundle for electrical machines wherein the portion of the conductor or conductor bundle which is to be installed in the grooves of a lamination packet of the machine, is enclosed with an insulation material containing mica which is bound with a high percentage by weight of binder, while the arm portion of the conductor or conductor bundle is enclosed with an insulation material containing only mica or mica bound with a low percentage by weight of binder.

States Patent Strauss et al.

[ Sept. 11, 1973 INSULATED COILS FOR ELECTRICAL MACHINES Inventors:Edmar Strauss; Siegfried Foth;

Hans-Jiirgen Kaltschmidt, all of Berlin, Germany LicentiaPatent-Verwaltungs-Gmbl-I, Frankfurt am Main, Germany Filed: Apr. 3,1972 Appl. No.: 240,639

Assignee:

Foreign Application Priority Data Apr. 3, 1971 Germany P 21 17 016.1

US. Cl. 174/120 SR, 310/260 Int. Cl. H0lb 7/02 Field of Search 174/120R, 120 SR;

References Cited UNITED STATES PATENTS 4/1969 Sheets 174/120 R DRYTAPE3,454,807 7/1969 Ganger 174/120 R Primary Examiner-E. A. GoldbergAttorney-George l-l. Spencer et a1.

[57] ABSTRACT An insulated conductor or conductor bundle for electricalmachines wherein the portion of the conductor or conductor bundle whichis to be installed in the grooves of a lamination packet of the machine,is enclosed with an insulation material containing mica which is boundwith a high percentage by weight of binder; while the arm portion of theconductor or conductor bundle is enclosed with an insulation materialcontaining only mica or mica bound with a low percentage by weight ofbinder.

8 Claims, 1 Drawing Figure Patented Sept. 11,1973

WET TAPE 1 A QWOVEN TAPE INSULATED COILS FOR ELECTRICAL MACHINESBACKGROUND OF THE INVENTION The present invention relates to theinsulation of coils formed of conductors or conductor bundles,respectively, for electrical machines, and to a method of insulatingelectrical coils, in which the conductors or conductor bundles aresurrounded by a micacontaining insulating material, are then installedin the machine, inpregnated with an impregnating resin, and thereafterhardened.

Particularly with respect to high voltage rotating machines, theconductors or conductor bundles are to an increasing degree beinginsulated by enclosing them in an insulating material, inserting theminto the lamination packet or stator grooves without impregnation, andthen impregnating the assembled coil and iron lamination packet, e.g. byimmersion into an impregnating resin.

The insulating material which is wound around the conductors orconductor bundles is usually in the form of a so-called "dry tape,"which consists of a carrier material, such as paper, rayon, polyesterfleece, or glass silk, for example, and fine mica without a binder, e.g.a resin, or fine or split mica, with as small a binder con.- tent aspossible, for example, about 3 to 8 percent by weight, which binderserves only to adhere the carrier material to the mica duringfabrication.

Although such tapes or bands are relatively absorbent, it has been foundthat perfect impregnation of the portion of the conductors or conductorbundles in the grooves of the lamination packet with an impregnatingresin, such as for example, an epoxy or polyester resin producesdifficulties in spite of the use of vacuum pressure impregnation,particularly for larger groove lengths. This is the case particularlywhen, for example, an impregnating resin containing anacceleratorcontaining impregnating resin is used whose reduction inviscosity cannot be set extremely low by increases in temperature duringthe impregnation process. The storage time at room or lower temperaturesis greatly reduced by the intermittent heating, so that the process isuneconimical.

SUMMARY OF THE INVENTION It is therefore, a primary object of thepresent invention to provide an insulated coil and a method ofinsulating such coils in which the coil impregnation is significantlyimproved even for the insulating material disposed within the grooves ofthe lamination packet, so that the above-mentioned difiiculties aresubstantially eliminated.

This object as well as others are accomplished according to the presentinvention by the provision of a coil in which the portion of theconductors or conductor bundles which come to lie within the grooves ofthe lamination packet of the machine is provided with an insulatingmaterial which contains mica bound with a large percentage by weight ofbinder and in which the coil ends and/or arm portions are provided withan insulating material which contains only mica or mica bound with a lowpercentage by weight of binder; and to a method of insulating suchcoils.

For the sake of clarity, the insulating material which has a highpercentage by weight of binder shall be referred to hereinafter as "wettape, while the insulating material having substantially no binder or alow percentage by weight of binder shall be referred to hereinafter asdry tape.

The wet tape," which may have any desired width, has a binder content ofapproximately 30 to 50 percent by weight. Thus a uniformly distributedresin binder is already available in sufficient quantity in the area ofthe lamination packet of the machine before the impregnation process.

The binder contained in the wet tape and the impregnating resin used forthe impregnation, for example a saturation resin, are so adapted to oneanother that they chemically react well together and have the sameprocess characteristics such as hardening time, hardening temperature,and simultaneous reaching of the minimum in vicosity during thehardening process, for example.

According to the present invention there is provided a veryadvantageous, homogeneous coil insulation for high voltage purposes bothin the area of the lamination packet of the machine as well as in thecoil end or arm portions. A long lamination packet groove does notconstitute a drawback for this type of insulation.

Thus all points of the coil including that portion in the laminationpacket of the machine are uniformly impregnated, coated and hardened sothat a perfect seal for the coil and of the lamination packet isobtained. As a result, the use of accelerator-containing insulatingtapes is no longer required, and the insulating materials for theswitching connections, detours etc. need no longer be selected with aview toward the proportion of accelerator used since the accelerator cannow be provided in the impregnating resin without shortening thestorability time due to the elimination of the otherwise required highincrease in temperature.

A further advantage of the present invention is that the percentage ofaccelerator proportion in the impregnating resin can easily be keptaccurately constant, in contrast to the difficulty encountered inmaintaining a uniform accelerator distribution in theacceleratorcontaining insulating tape. Thus the reactions of theimpregnating resin can also be unequivocally predetermined.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE schematically illustrates apartial longitudinal sectional view of a top portion of the coilaccording to the present invention in which both the wet tape and drytape portions are shown together with a transition zone of the coil.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A portion of a coil 1 for anelectrical machine as illustrated in FIG. 1 shows part of a conductor orconductor bundle 1' and only a cut-away part of the insulation for thesake of clarity. The coil 1 has a first or core portion 2 which extendsfor a length L and a coil end or arm portion 3 which extends for alength L, A part of the core portion 2 of the coil comes to lie withinthe grooves of a lamination packet of the machine (not shown). This partof the core portion has a length L A transition zone having a length L,is situated between the part of the core portion 2 having a length L,and the coil and or arm portion 3 which has a length L, The transitionzone forms part of the core portion 2.

According to the present invention, a wet tape 4 is wound around thecore portion 2 over the length L,, while the coil end or arm portion 3has a dry tape 5 wound around it over the length L,,. The transitionfrom dry tape to wet tape advisably takes place in a transition zone orcore discharge area 7 which has a length L.,. In order to assure auniform transition, the contact line 8 from dry tape to wet tape 4 isformed during the course of wrapping about the arm portion 3 and coreportion 2, respectively. That is these tapes are wound so thatsubsequent layers thereof are offset with respect to each other.

It is advantageous, as shown in the drawing, if a woven tape ofinsulating material is wrapped around the entire conductor or conductorbundle 1 before the application of the insulating material 4 and 5. Ifit is intended to preliminarily prepress the core portion 2 over thelength L,, the woven tape 9 may be eliminated at the core portion 2.

Generally, the wet tape 4 is prepressed or tensioned directly before andduring the installation of the coil in the machine in order to obtain agood packing of the binder.

After installation of the coil and during the impregnation, e.g. duringa vacuum pressure impregnation, the impregnating resin can penetrateinto the area of the wet tape 4 due to the valve effect of the dry tape5 and the wick effect of the woven tape 9. The quantity of impregnatingresin which would otherwise be required for a dry tape is by far not ashigh when wet and dry tape areused because the high proportion of binderin the wet tape serves as a certain percentage of the needed resin. Thusit is assured in any case that sufficient resin is present in the coreportion of the conductor or conductor bundle, which is under a highdielectric stress, so that the desired homogeneous isulation isproduced.

Although the use of wet tapes or broad materials rich in binder seems tobe contradictory at first because the material is permeable for theimpregnating resin only to a very slight degree even during a vacuumpressure impregnation, it is possible, according to the presentinvention, to obtain a perfect insulation sheath for high voltagepurposes.

At a specific example of a coil for a 6-kilovolt dynamo-electric machineinsulated according to the invention the above mentioned length L L andL measured in centimeters: L, =l00, 100 and L =5. The wet tape 4consisted of a carrier material of glasssilk and fine mica with 40percent by weight of an epoxy resin as a binder. The wet tape 4 waswound with no overlap around the conductors to nine layers. The dry tape5 also consisted of a carrier material of glasssilk and fine mica with 4percent by weight of an epoxy resin as a binder. The dry tape was woundwith an overlap of one half around the conductors to four layers. Thewoven-tape 9 was made of glass-silk. The impregnating resin used was anepoxy resin, the hardening lasted for 24 hours and the hardeningtemperature was at 155 C.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

We claim:

1. In an insulated conductor or conductor bundle, for electricalmachines in which the conductor or conductor bundle includes a firstportion which is to lie within the grooves of a lamination packet of themachine and an arm portiOn which is connected to thefirstportion, and inwhich the conductor or conductor bundle is enclosed in a micacontaining.insulating material, before being installed in the machine andimpregnated with an impregnating resin which is subsequently hardened,the improvement wherein the insulating material provided for said firstportion of the conductor or conductor bundle which is to lie within thegrooves of the lamination packet of the machine includes mica which isbound with a high percentage by weight of binder, and the insulatingmaterial provided for said arm portion includes mica and from zero to atmost a very small percentage by weight of binder relative to thepercentage by weight of binder in the insulating material of said firstportion.

2. Th insulated conductor or conductor bundle as defined in claim 1wherein the conductor or conductor bundle further includes a dischargeportion between the first portion and the arm portion, and wherein thedischarge portion forms a transition zone from the insulating materialhaving a high percentage by weight of binder to the insulating materialhaving from zero to at most a very small percentage by weight of binder.

3. The insulation conductor or conductor bundle as defined in claim 2wherein the insulating materials in the transition zone form offsetlayers with respect to each other.

4. The insulated conductor or conductor bundle as defined in claim 1wherein a woven tape is provided between the conductor or conductorbundle and the insulating materials.

5. The insulated conductor or conductor bundle as defined in claim 1wherein said insulating material having a high percentage by weight ofbinder is prepacked.

6. The insulated conductor or conductor bundle as defined in claim 1wherein the percentage by weight of binder in said insulating materialcontaining a high percentage of binder is between 30 and 50 percent byweight.

7. The insulated conductor or conductor bundle as defined in claim 1wherein said insulating material containing mica and from zero to atmost a very small percentage of binder contains only mica.

8. The insulated conductor or conductor bundle as defined in claim Iwherein said insulating material containing mica and from zero to atmost a very small percentage of binder contains 3-8 percent binder byweight.

1. In an insulated conductor or conductor bundle, for electricalmachines in which the conductor or conductor bundle includes a firstportion which is to lie within the grooves of a lamination packet of themachine and an arm portiOn which is connected to the first portion, andin which the conductor or conductor bundle is enclosed in amica-containing insulating material, before being installed in themachine and impregnated with an impregnating resin which is subsequentlyhardened, the improvement wherein the insulating material provided forsaid first portion of the conductor or conductor bundle which is to liewithin the grooves of the lamination packet of the machine includes micawhich is bound with a high percentage by weight of binder, and theinsulating material provided for said arm portion includes mica and fromzero to at most a very small percentage by weight of binder relative tothe percentage by weight of binder in the insulating material of saidfirst portion.
 2. Th insulated conductor or conductor bundle as definedin claim 1 wherein the conductor or conductor bundle further includes adischarge portion between the first portion and the arm portion, andwherein the discharge portion forms a transition zone from theinsulating material having a high percentage by weight of binder to theinsulating material having from zero to at most a very small percentageby weight of binder.
 3. The insulation conductor or conductor bundle asdefined in claim 2 wherein the insulating materials in the transitionzone form offset layers with respect to each other.
 4. The insulatedconductor or conductor bundle as defined in claim 1 wherein a woven tapeis provided between the conductor or conductor bundle and the insulatingmaterials.
 5. The insulated conductor or conductor bundle as defined inclaim 1 wherein said insulating material having a high percentage byweight of binder is prepacked.
 6. The insulated conductor or conductorbundle as defined in claim 1 wherein the percentage by weight of binderin said insulating material containing a high percentage of binder isbetween 30 and 50 percent by weight.
 7. The insulated conductor orconductor bundle as defined in claim 1 wherein said insulating materialcontaining mica and from zero to at most a very small percentage ofbinder contains only mica.
 8. The insulated conductor or conductorbundle as defined in claim 1 wherein said insulating material containingmica and from zero to at most a very small percentage of binder contains3-8 percent binder by weight.